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Non-Controlling Interests - Financial Position of Non-Controlling Interests (Details) - CAD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Disclosure of subsidiaries [line items] |  |  |
Current assets | $ 1,902 | $ 1,341 |
Current liabilities | (935) | (1,117) |
Total equity | 3,436 | 4,062 | $ 4,134
Non-controlling interests | 1,084 | 1,101 |
TransAlta Renewables Inc. |  |  |
Disclosure of subsidiaries [line items] |  |  |
Current assets | 743 | 293 |
Long-term assets | 2,913 | 3,409 |
Current liabilities | (364) | (152) |
Long-term liabilities | (987) | (1,237) |
Total equity | (2,305) | (2,313) |
Non-controlling interests | $ (948) | $ (941) |
Ownership and voting rights percentage | 39.90% | 39.60% |
TransAlta Cogeneration, L.P. |  |  |
Disclosure of subsidiaries [line items] |  |  |
Current assets | $ 69 | $ 41 |
Long-term assets | 323 | 328 |
Current liabilities | (78) | (27) |
Long-term liabilities | (37) | (19) |
Total equity | (277) | (323) |
Non-controlling interests | $ (136) | $ (160) |
Ownership and voting rights percentage | 49.99% | 49.99% |
TransAlta Cogeneration, L.P. | Coal facility |  |  |
Disclosure of subsidiaries [line items] |  |  |
Ownership and voting rights percentage | 50.00% |  |

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